One intriguing possibility – and one that's it's very difficult to either prove or disprove – is that this is a warrant canary triggered by pressure on TrueCrypt's developers by the feds to backdoor the software – which is favoured by the likes of Edward Snowden and his journo pals. Effectively, it would be a signal to the world that something is not right, without breaching any gagging order that may also be in place.

It could even be in response to a threat to unmask the development team.

"Somebody was about to de-anonymize the Truecrypt developers, and this is their response," suggested Prof Green.

Veteran security world watcher Graham Cluley said: "Whether hoax, hack or genuine end-of-life for TrueCrypt, it’s clear that no security-conscious users are going to feel comfortable trusting the software after this debacle. It’s time to start looking for an alternative way to encrypt your files and hard drive."

The outlook for those who rely on TrueCrypt to encrypt their drives and/or files just became overcast with doubt.

Johannes Ullrich of the SANS Technology Institute recommended FileVault and LUKS, for Mac OS X and Linux users, respectively, as potential alternatives. "Sadly, these are not compatible with each other. You will need to find a replacement for portable media that need to move between operating systems. PGP/GnuPG comes to mind as an option," he advised.

An earlier list of alternatives to TrueCrypt put together by security expert The Grugq can be found here.

Amichai Shulman, CTO at Imperva, said even before this week's events that TrueCrypt was ill-suited to use within enterprises.

"There is a place for a disk encryption solution independent of operating system type and operating system provider in general," Shulman said. "Whether TrueCrypt is the right solution, given the anonymous nature of its developers, I’m not sure."

Shulman added that the end-of-XP support provides a plausible reason to discontinue the TrueCrypt project.

"TrueCrypt was created in order to provide disk encryption for operating systems that do not have built-in support for it. Currently the only one is Windows XP and since it is 'no longer safe' to use it, there’s no point in maintaining an encryption solution for it." ®